” Invisalign, a San Jose company, uses 3-D printing to make each mouthful of customized, transparent braces. Mackenzies Chocolates, a confectioner in Santa Cruz, uses a 3-D printer to pump out chocolate molds. And earlier this year, Cornell University researchers used a 3-D printer, along with injections of a special collagen gel, to create a human-shaped ear.

Once a science-fiction fantasy, three-dimensional printers are popping up everywhere from the desks of home hobbyists to Air Force drone research centers. The machines, generally the size of a microwave oven and costing $400 to more than $500,000, extrude layer upon layer of plastics or other materials, including metal, to create 3-D objects with moving parts.

Users are able to make just about anything they like: iPad stands, guitars, jewelry, even guns. But experts warn this cool innovation could soon turn controversial — because of safety concerns but also the potential for the technology to alter economies that rely on manufacturing.”